200 grn SST Performance

Had the opportunity to take a small Mule Deer buck this week and has some concerns with bullet performance and wanted to get some input.

The first shot was from an awkward offhand position at 50-75 yards and was a solid gut shot, landing about 6" behind the vitals (needed to fill the tag or I would have waited for a better shot). My second shot was a running shot at about 100 yards with a better rest and was the picture perfect double lung shot behind the shoulder, not destroying any meat. This shot dropped him.

When I got to to where he lay I was surprised to find that the neither exit wounds were much larger than 1".

Any thoughts on why these bullets didn't open up anymore? Should these have opened up more? My understanding is that they are not bonded or designed for penetration.